The singing-activity of the cricket Teleogryllus commodus is under circadian control and it can be synchronized by light/dark changes so that the males begin to stridulate every day 1-2 h before the onset of darkness and stop singing 3-4 h before light-on. In the proposed work the Zeitgeber light/dark change will be replaced by a temperature cycle: 12 h of temperature A will be followed by 12 h of temperature B in constant light, and the following questions are asked: How large has a temperature step to be for a synchronization of stridulatory activity to happen? Do the crickets sing mainly in the higher or in the lower temperature phase? In addition, the time necessary to reach the next temperature level will be varied from 5 min to 1 h. Should the entrainment procedure succeed, then the next step will be to cause arhythmical stridulation in the crickets by severance of the two optic lobes and to try to resynchronize stridulation by exposing the operated crickets to temperature cycles. In a further experiment, several behavior patterns like singing, locomotion, feeding and drinking will be recorded simultaneously and under various light regimes in order to demonstrate the coordinating capacity of the biological clock.